The present invention relates to a redundant control device and a network system, more particularly, to a master switching control technique of the redundant control device.
In general, in a network, a redundant configuration is adopted in such a manner that communication is not stopped due to the fact that a line or device is broken. In a plurality of redundant network repeaters, respective network repeaters are connected through a plurality of downstream devices and ports. Further, some network repeaters each having the large number of effective ports (the number of linked-up ports among the ports connected to the downstream devices) operate as an operation system. The above-described technique is disclosed, for example, in JP-A-2005-354362. The number of effective ports is compared to perform a priority determination among the plurality of redundant network repeaters, thereby switching an operation system and a waiting system.
Further, as a mechanism for preventing a useless switchover between the Operation system and the waiting system, switching prevention time is provided. Through the process, a technique for delaying a switchover is disclosed, for example, in Brocade/FastIron Configuration Guide Supporting IronWare Software Release 07.2.02, P477, “Changing the hold-down interval”